Absolute value transmitter acting as a rotation transmitter for registration of a steering angle of a motor vehicle

ABSTRACT

A rotary transmitter for registration of the steering angle of a motor vehicle, with a transmitter component ( 49 ) on which is provided a coding ( 51 ) of a predetermined number n of locally sequentially digital words (W i ) with a width of m bits (b 1 , b 2 , . . , B m ) in m adjacent to each other tracks, at least one detector ( 55 ) for essentially simultaneous registration of the individual bits (b 1 , b 2 , . . . , B m ) of a digital word (W i ), whereby the transmitter component ( 49 ) and at least the one detector ( 55 ) are movable relative to each other, and with an evaluation unit ( 11 ) to which is conducted the signal of at least the one detector ( 55 ). The evaluation unit ( 11 ) ascertains the absolute position of the transmitter component ( 49 ) relative to at least the one detector ( 55 ), at least one time, by evaluation of a predetermined number (p) of sequentially detected digital words (W i ), whereby the evaluation unit ( 11 ) assigns to a detected p-measure (W i , W i+1 , . . . , W i+p−1 ), consisting of the predetermined number (p) of sequentially detected digital words (W i ), a defined position value of the transmitter component ( 49 ) relative to at least the one detector ( 55 ). The coding is hereby designed in such manner that all sequences (W i , W 1+1 , . . . , W i+p−1 ) from among the sequential words (W i ) consisting of the predetermined number (p) are uniquely defined at least within a predetermined uniquely defined area (I. II) of coding ( 51 ) and that within each uniquely defined area (I, II) the digital words (W i ) are not uniquely defined.

The invention concerns a digital absolute value transmitter,specifically a rotation transmitter for registration of the steeringangle of a motor vehicle.

Highly accurate registration of the steering angle gains ever growingimportance in modern motor vehicles, whereby, for example the steeringangle is needed in regard to active dynamic moving mechanisms forcontrol or regulation of the moving gear state or moving gear behavior.In practically all instances, the highly accurate registration of theabsolute value of the steering angle is needed. This, however, requiresextremely accurate absolute value transmitters, with generally costlyconstruction and correspondingly high expenditure.

Known digital absolute value transmitters (for example JP 4-1522 A)which are suitable as rotation transmitters for registration of theabsolute rotation angle, have, as a rule, an encoding, which, byscanning each word, i.e. bits in one line, permits the determination ofa value assigned to said word. It is, however, of disadvantage withrespect to such digital absolute value transmitters that the words musthave a relatively large width in order to ensure adequate resolution. Inthis context, a digital absolute position encoder or encoding method isknown from DE 195 45 949 A1, in which the number of the required tracksfor providing an absolute value transmitter is reduced by a single-stepcode; said benefit, however, is only obtained by utilization of severaldetectors per track. This means higher circuit-engineering expenditure.

That also applies with respect to absolute value transmitters which haveonly one single track, and which concurrently scan several bits of thetrack, whereby the digital words of a code are sequentially connected inthe track (for example JP 08-122099 A; DE 40 22 503 C1; DE 195 18 664C1).

The above specified absolute value transmitters permit immediatedetermination of absolute position in each position, but require highexpenditure.

Relative value transmitters can be realized more simply and morecost-favorable, but in such case an initialization process is necessarybefore operating the system for calibration of the relative valuetransmitter. To that end, for example, the steering system or thesteering wheel must be brought into a defined position, staring fromwhich, a determination of the absolute values of the steering angle canbe made via relative registration of the steering angle. Although it is,in fact, possible to also store the starting value (initializationvalue) for determination of the absolute value so that if the systemloses tension, the value remains preserved, the problem rests in thefact that if the system is switched off, steering movements are nolonger registered and, consequently, following activation of the system,an initialization process would have to be gone through.

In addition, absolute value transmitters are known which linkincremental and absolute coding- or decoding methods (for example EP 0530 176 A1; EP 0 545 701 A1). As a rule, one incremental code is usedcovering the entire to be registered range and one absolute code at oneor several selection positions. The absolute positions are registered bymeans of a first detector as with conventional absolute valuetransmitters, whereby, however, only a small width for the digital wordsis required. Starting from the then known absolute position, it is thenpossible, by means of the incremental code, which is being scanned byanother detector, to determine the respective absolute position whenthere is a relative movement of code and detector.

This type of absolute value transmitter also required a relatively highexpenditure and can only register correctly the absolute position, afterlosing power, if the first absolute code had been reached. In motorvehicle technology this is not permissible for reasons of safety.

The invention is therefore based on the object to provide an absolutevalue transmitter, specifically a rotation transmitter for registrationof the steering angle of a motor vehicle, which can be realized assimply as possible and cost-friendly and which ensures, at the sametime, adequate operating safety, specifically after the system has lostpower.

The invention solves this object with the characteristics of Patentclaim 1.

By the at least one-time determination of the absolute rotation angle byevaluation of a pre-determined number p of sequentially detected digitalwords (W_(i)) there results the benefit of substantially lower requiredword width. For first-time determination of the absolute value,overtravel of p words is necessary, so that, to that end, thetransmitter component must, initially, be moved by p-times theresolution. However, after first-time determination of the absolutevalue, the maximal resolution is then again reached, i.e. the absolutevalue can be exactly determined with each overtravel of a word (W_(i)).All sequences (W_(i), W_(i+1), .W_(i+p−1)) consisting of predeterminednumbers (p) of sequential words (W_(i)) of the encoding must be, to thatend, uniquely defined, at least within a predetermined uniquely definedrange of the encoding. Without complying with this requirement, a givenp-measure cannot be assigned a defined absolute value. In contrastthereto, within each uniquely defined range, the digital words (W_(i))need not be uniquely defined.

In the preferred specific embodiment of the invention, at least one ofthe following conditions is complied with:

a) in each instance, two adjacent words, W_(i), W_(i+1) have differentvalues, i.e. W_(i) is not equal to W_(i+1);

As a result of this, step recognition is made possible by the evaluationonly of the signal generated by encoding, so that synchronized scanningcan be relinquished;

b) the respective words W_(i−1) and W_(i+1), adjacent to the word W_(i);have different values, in other words W_(i−1) and W_(i+1) are not equal;This permits recognition of change in the movement direction byevaluation of only the signal generated by the encoding; without saidrequirement it would not be possible, in case of a change in thedirection of the movement, after prior registration of the wordsW_(i−1), W_(i), . . . , W_(p−2,) W_(p−1) to determine whether in caseW_(p−2)=W_(p) the value W_(p) was produced by a movement in the samedirection or by a movement in the opposite direction; that applies atleast if the evaluation unit realizes the p-measure in form of a firstin—first out register, whereby each new word W_(i) is always “inserted”in the register of the fixed length p from the same end and that,respectively, prior to the insertion, the last word is dropped,independent of whether prior to registration of said W_(i) a change tookplace in the direction of movement.

c) no p-measure (W_(i), W_(i+1, . . . ,) W_(i+p−1)) may exist within atleast one uniquely defined range of the encoding as mirror-imagep-measure (W_(i+p−1), W_(i+1), W_(i)) in other words (W_(i), W_(i+1), .. . , W_(i+p−1)) is not equal to W_(i+p−1−k), . . . , W_(i+1−k),W_(i−k)); Otherwise it could not be determined by evaluation alone fromthe signal generated by the encoding whether the respective p-measurewas generated in overtravel from one or the other direction; Thus,recognition of the absolute movement direction is hereby facilitated.

This condition could only be dropped when in each instance recognitionof the movement direction would be ensured by providing an additionaldevice.

According to one specific embodiment of the invention, the evaluationunit can in each instance effect the determination of the absolute valueby allocating the respective predetermined value to the actualp-measure.

The possibility, however, also exists, to effect said possibility ofabsolute value determination only once or at given intervals, or forcertain reasons, and to determine future absolute values byincrementation or decrementation. Thus, only one evaluation is necessaryfor step recognition and for recognition of a change in the direction ofmovement.

A change in the direction of movement can be effected in simple fashionby satisfying the above mentioned condition b) by evaluation of thewords W_(p−2) and W_(p):

If both words agree, then a change in the direction of movement hastaken place.

In one specific embodiment of the invention, which affords added safety,the absolute value can be determined both by evaluation of the p-measureas well as by incrementation/decrementation of the prior value and withlack of agreement, an error signal can be generated.

In the preferred specific embodiment of the invention, p=3 sequentialwords W_(i) are evaluated. Combined with a word width m=3 (3 bit) of thedigital words, an excellent compromise results between sufficientencoding length (permissible n number of digital words using the abovementioned conditions) and thus the attainable resolution and thecalculation expenditure for the evaluation, including the requiredmovement path for the first-time determination of the absolute positionvalue, for which at least p (here p=3) digital words must be registeredby at least the one detector.

According to the preferred specific embodiment of the invention, theencoding comprises at least two connecting areas, whereby theaforementioned encoding conditions are satisfied both within the areasas well as at the interfaces. Encoding within the areas is preferablyidentical and extends in the same direction.

According to another specific embodiment of the invention, there isprovided, for step recognition and/or recognition of the rotationdirection and/or a change in rotation direction an additional track tothe tracks for the digital words (W_(i)) with sequential values, logical[value] “zero” and logical [value] “one”, or a track for the digitalwords of the encoding is designed in this manner.

For scanning the track with alternating sequence of values, logical“zero” and logical “one” there may preferably be provided two detectors,staggered by half a step, whereby the evaluation unit determines therotation direction and/or a change in the direction of rotation from thephase displacement of the sensor signals. In addition, the evaluationunit is able to determine from the signal of one or both sensors whethera step has taken place and can, dependent thereon, perform a scanning ofthe digital word.

Encoding can be designed in such manner that within at least oneuniquely defined area for one, several or all sequences (W_(i), W_(i+1),. . . , W_(i+p−1)) of the encoding there also exists the respectivemirror-image sequence of the encoding (W_(1+p−1), . . . , W_(i+1),W_(i)) and that the evaluation unit determines from the direction of therotation and the detected p-measure, the absolute value. This producesmaximal length of encoding with assured step recognition.

Equivocation of encoding with several uniquely defined areas outside theuniquely defined areas may be done, according to the invention, byproviding one registration device for unrefined registration of theabsolute position and additional evaluation of its position signal. Theaccuracy of said unrefined registration device must in each case bebetter than the difference of each of the position values correspondingto at least two encoding areas. The evaluation unit is then able todetermine the exact absolute position value by evaluating the signal ofat least one detector for registration of the encoding and the signal ofthe approximate registration device with the accuracy and the resolutionof the encoding.

In the preferred specific embodiment of the invention, the evaluationunit undertakes the following steps in ascertaining the exact absoluteposition value:

a) determination of the actual signal of the registration device forapproximate registration of the corresponding position value (α_(a));

b) determination of a lower and upper barrier (α_(a)−δ; α_(a)+δ) of apermissible tolerance range for the ascertained position value (α_(a)),whereby the width (2δ) of the tolerance range is smaller than eachuniquely defined range of the encoding of the transmitter component;

c) determination of the multi-valued position value α_(r) by evaluationof the signal of at least one of the detectors reading the encoding;

d) determination of the corrected absolute value α_(r,corr.) accordingto the formula:

α_(r.corr.) =INT[(α_(a)+δ)/α_(a.max)]_(x) α _(r.max)+α_(r)

for α_(r)<α_(r.max)/2

α_(r.corr) =INT[(α_(a) −d)/α_(r.max)]×α_(r.max)+α_(r)

for α_(r)>α_(r.max/)2

α_(r.max) stands for the maximally possible value for the absolute(multi-valued) position by evaluation of the p-measure.

In the preferred specific embodiment, the evaluation unit examineswhether the ascertained absolute position value α_(r.corr) lies withinthe permissible tolerance range α_(a−)δ<α_(r.corr)<^(α)a+δ and producesin case of error an error signal and/or performs a compensation of theapproximate registration device. For example, the evaluation unit can,to that end, determine the difference between the ascertained absolutevalue (α_(r.corr)) and the position value (α_(a)) and deposit same in apreferably non-volatile memory and use it as correction value for futuredeterminations of the position value (α_(a)).

According to one specific embodiment of the invention, the absolutevalue transmitter is designed as rotation transmitter, whereby thetransmitter component is rotatably connected with a component whoserotation angle is to be registered, for example, the steering shaft of amotor vehicle or a component connected with same. The encoding providedon the transmitter component is preferably endless and is arranged onthe outer circumference of the transmitter component. At each interface,the requirements according to claim 2 are complied with.

Additional specific embodiment are apparent from the sub-claims.

In the following, the invention is explained in more detail, using oneof the exemplary embodiments depicted in the drawing:

FIG. 1 shows a perspective, exploded representation of components of asteering system, essential for understanding the invention, with adigital absolute value transmitter according to the invention.

FIG. 2 shows a longitudinal section through the assembled steeringsystem according to FIG. 1 and

FIG. 3 shows a schematic representation of a permissible encodingaccording to a preferred specific embodiment of the invention.

The components illustrated in FIG. 1 involve, essentially, the steeringwheel 1 and a multi-function unit 3, which, among others, includes anabsolute value transmitter 5 for registration of the steering angle.

The multi-function unit 3 consists of a stationary housing component 7,which consists of the two halves 7 a and 7 b. The stationary housingcomponent 7 is designed in such manner that it can be pushed onto asteering column 9 (FIG. 2) and surrounds same.

Into the half 7 b of the housing component 7 can be integrated, as shownin FIG. 1, additional components such as steering column switch,ignition lock and similar. Also, an electronic unit is provided in theinterior of half 7 b of housing component 7, which comprises thenecessary circuits on the stationary side of the multi-function unit 3.This may involve details of circuits for the steering column switch, theignition lock and data transmission from and to the operating units 13provided at the steering wheel and also the evaluation unit for theabsolute value transmitter according to the invention.

Furthermore, the multi-function unit 3 has a housing component 15, whichis attachable to the reverse side 1 a of the central area of thesteering wheel and which serves for acceptance of a transmitter/receiverunit 17, comprising the required circuits of the functional units 13arranged at the steering wheel 1 for transmission of data from and tothe steering wheel.

As can be seen from FIG. 2, the circuits of the electronic unit 11 arearranged on a plate 19, which is fastened (not shown in detail) in theinterior of half 7 b of housing component 7. The interior space of half7 b is essentially tightly sealed by the back wall, extending radiallyvis-a-vis axis A of steering column 9, of half 7 a of the housingcomponent 7. For that purpose, half 7 a is connected with half 7 b bymeans of engagement elements 23 formed onto 7 a, whereby the engagementelements 23 engage with corresponding recesses 25 in half 7 b.

The backwards area of half 7 b of housing component 7 encloses, with itscentral recess, the steering column 9 and can be connected, by means ofa clip 27, torsion-proof with the relative to the remainder of thevehicle stationary [with the steering column non-rotatable] outside ofthe steering column 9. The steering wheel 1 is connected, by means of anut 29, with steering shaft 31, which is equipped, for that purpose inits foremost region with screw thread. Furthermore, a bushing 33 isconnected torsion-proof with the steering wheel 1, said bushingenvelopes the steering column 9. On the bushing 33 is attached,torsion-proof a first gear wheel 35, which is thus rotatable togetherwith the steering wheel 1.

On the backwards side of the plate 19 is arranged a plunger coil 37 of aplunger coil unit 39, serving as registration unit for approximateregistration of the absolute steering angle. The plunger coil 37 canhave connection terminals (not shown here) for the coil, which engagewith contact bores in plate 19 and which can be welded in place at thesame time with the other modular electronic components.

The plunger coil unit 39 also comprises a thread spindle 41 which isretained, with its posterior end rotatably in the rear wall of theplunger coil 37. On the thread spindle 41 is retained a plunger element43, whereby the plunger element 43 is fitted with a thread bore, whichcooperates in such fashion with the exterior thread of the threadspindle 41 that with a rotation of the thread spindle 41 the plungerelement 43 is moved translatorially into the coil 37 and out of same.The plunger element 43 preferably consists of ferrite material and is,additionally, guided in its displacement direction through the interiorwall of the plunger coil 37.

At the anterior end of the thread spindle 41, a second gear wheel 45 istorsion-proof arranged which mates with the first gear wheel retainedtorsion-proof on the bushing 33.

In this manner, the rotational movement of steering wheel, and thetherewith torsion-proof connected bushing 33, is translated into atranslatorial movement of the plunger element 43 of the plunger coilunit 39.

The evaluation unit 11—(only this component of the electronic unit is ofimportance for understanding the invention),—provided on the plate 19assesses induction changes of the plunger coil unit 39 as result of thetranslatorial movement of the plunger element 43 and thus converts therotational movement of the steering wheel into a correspondingelectrical signal. This may, of course, involve an analog or a digitalsignal.

In addition to the above described registration device for approximateregistration of the steering angle, the absolute value transmitter 5,according to FIG. 1, comprises a device 47 for accurate registration ofthe steering angle. This device consists, on the one hand of atransmitter component, designed in form of a ring, on whosecircumferential surface is provided a coding 51. Same consists of threetracks in circumferential direction, in which are respectively arranged3 markings 53 extending in axial direction. The respective markings inone line represent digital words W_(i), with 3 bits each. Any respectivesequential words Wi are preferably provided in circumferential directiondirectly adjacent to each other.

The ring 49 is pushed onto bushing 33 and held torsion-proof on same.With a turn of the steering wheel 1, the ring 49 is thus also turnedtogether with the bushing 33.

As is apparent from FIG. 2, the markings 53 of each track provided onthe circumferential surface of ring 49 are respectively registered by adetector 55. The three detectors may for example be designed asHall-sensors which register, accordingly, magnetically designed markings53 of coding 51. The signal of detectors 55 is likewise conducted to theevaluation unit 11.

Instead of the three detectors 55, it is, of course, possible to alsoemploy one single detector, which facilitates separate registration ofmarkings 53 of the three tracks with sufficient speed. Marking 53 anddetectors 55 can also be realized in any other manner, for example asoptical markings and optical detectors. By appropriate signalevaluation, it is, of course, self-understood, that also only one singlesensor may be provided, which scans the markings 51 of all tracks.

In order to obtain, for example, a resolution of 1.5°, 240 digital wordsW_(i) are required.

With conventional digital absolute value transmitters, a coding isgenerally employed, which, by scanning each word, i.e. the bits in oneline, facilitates the determination of a value assigned to said word.With the forenamed required resolution of 1.5°, thus 8 bits would beneeded in order to instantly be able to determine via one singlescanning of a word W_(i) the angle of rotation. This, however, would beconnected with disproportionately high expenditure, both in preparingthe coding as well as in manufacturing the ring 49 and also in therealization of the detectors 55.

According to the invention, it is therefore proposed, to ascertain theabsolute position of the transmitter component or the absolute rotationangle by evaluation of a pre-determined number of p sequentiallydetected digital words W_(i), i.e. by the evaluation of one eachp-measure (W_(i), W_(i+1,) . . . , W_(i+p−1)).

The in represented specific embodiment, the width of the words W_(i) isequal to three bits.

In actual practice it has been demonstrated that in this case by theevaluation of each three sequential digital words W_(i)—which may thentake on the values from 0 to 7 - - - (2³−1=7) a resolution of 1.5° isreadily realizable, whereby the maximally overtravelled angle areaamounts to 4.5° for determination of the absolute angle (depending uponthe design of the detectors and the markings on the transmittercomponent).

This ensures, even with a first-time start-up of the absolute valuetransmitter 5, that following overtravel of an angle area (in the samedirection) of 4.5°, the absolute angle of the steering shaft isdeterminable with a resolution and an accuracy of better than 1.5°.

According to the invention, coding is selected in such manner that thealready mentioned conditions are complied with, whereby p=3 is to beused here:

a) each two adjacent words, W_(i) W_(i+1) have different values, inother words W_(i) does not equal W_(i+1) (step recognition);

b) the words W_(i−1) and W_(i+1) adjacent respectively to a word W_(i),have different values, in other words, W_(i−1) and W_(i+1) are not equal(recognition of change in the direction of rotation);

c) each sequence (W_(i), W_(i+1), W₁₊₂) of respectively 3 sequentialwords of the coding is, at least within a predetermined area of thecoding, uniquely defined, in other words, the following applies: (W_(i),W_(i+1), . . . , W_(i+2)) is not equal to (W_(k), W_(k+1), W_(k+2)) withrespect to i not equal to k (uniquely defined coding within one area ofcoding);

d) no sequence (W_(i), W_(i+1), W_(i+2)) may exist, in at least oneuniquely defined area of the coding as mirror-image sequence (W_(i+2),W_(i+1), W_(i))—in other words, the following applies: (W_(i), W_(i+1),W_(i+2)) is not equal (W_(i+2−k), W_(i+1−k), W_(i−k)) (recognition ofthe absolute rotation direction).

Taking into account all of these conditions, the result, however, isthat with the employed word width of 3 bits, the number of possiblewords is insufficient, so that the entire coding at the circumference ofring 49 must be divided into two areas I, II (FIG. 3) which each coveran angle of 180°.

In each of the two areas I, II the same coding is used, whereby in bothcoding areas the same coding direction exists. At the two interfaces 60,62, the aforementioned conditions are likewise complied with.

With respect to the example for coding of ring 49, depictedschematically in FIG. 3 there thus result 120 digital words W_(i) perarea, which corresponds to the required resolution of 1.5°.

Since the plunger coil unit 39 and the ring 49 are coupled mechanicallywith the steering shaft 31, there is a fixed relationship between thesignal of the plunger coil unit serving as approximate registrationdevice and the signals of the detectors 55. The equivocation of thesignals of the detectors, which respectively generate 3-bit words can beeliminated in the following manner by additional evaluation of thesignal of the plunger coil unit.

As starting point, a situation is selected in which the absolute valuetransmitter 5 is connected, for the first time, to the energy sourceand, consequently, not one single digital word W_(i) of coding 51 hasbeen registered by scanning of marking 53 via detectors 55.

Nevertheless, in said starting situation, the signal S_(T) of theplunger coil unit 39 is passed to the evaluation unit 11, and can beevaluated by the evaluation unit. To that end, for example, theevaluation unit 11 compares, for example, the momentary value of thesignal S_(T) of the plunger coil unit 39 with a prior knowncharacteristic curve α_(a)(S_(T)) which may be stored, for example asfunctional dependence or in form of digitalized values in the evaluationunit 11, and establishes in this fashion an approximate value for theangle of rotation.

If the angle of rotation α is required by other components of the motorvehicle, for example by the steering unit of a dynamic moving gear, thensaid approximate value (α_(a)(S_(T)) may initially be emitted by theabsolute value transmitter to said steering unit.

If then at any random point in time, the steering column is rotated andif during the rotation an angle surface of at least 4.5° in the samedirection is overswept, then the evaluation unit can already determinefrom the three first registered digital words W_(i), i.e. the first 3digit measurement, the absolute rotation angle with the accuracyspecified by the coding.

In order to eliminate the equivocation of the 3-digitmeasurement—initially, starting from a straight-on position, it is notknown in what position the steering column is located—the evaluationunit first determines an admissible tolerance range for the approximateangle α_(a) ascertained from the signal S_(T) of the plunger coil unit.

For that purpose, a value for an error barrier α is, for example, storedin the plunger coil unit. With it, the evaluation unit 11 determines thetolerance range for α_(a)−δ<α_(a)+δ, whereby the width 2d of thetolerance range is smaller than each of the two uniquely defined areasof the coding of the transmitter component, i.e. smaller than 180°.

Furthermore, the evaluation unit 11 determines by evaluating the first3-digit measure of the first (multi-valued, but accurate) rotation angleα_(r), which lies in the area [0; 180].

Finally, the evaluation unit 11 ascertains whether the value α_(r) issmaller than, identical to or larger than half the mail possible valuefor the rotation angle α_(r). Depending upon this check, the evaluationunit 11 can determine the corrected value α_(r.corr.) by evaluating thefollowing specifications:

α_(r.corr) =INT[(α_(a)+δ)/α_(r.max)]×α_(r.max)+α_(r)

for α_(r.max)</2

α_(r.corr.) =INT[(α_(a)−δ)/α_(r.max)]×α_(r.max)+α_(r)

for α_(r.max)>/2

INT designates the integral-division.

For example, evaluation of the signal S_(T) of the plunger coil unitproduces a value of α=535° and evaluation of coding produces a value ofα_(r)=3°, consequently, the condition α_(r)=3<90° is satisfied. This inregard to the first of the aforementioned conditions and thereby toα_(r.corr)=INT[555°/180°]×180°+3=543°, whereby the error barrier of theapproximate registration for the absolute angle was selected at δ=20° bymeans of the plunger coil unit.

Following said initial registration of the exact steering angle, in thefuture the absolute value can be determined by detection of individualsteps and changes in the direction of rotation via simple incrementationor decrementation. Needless to say, of course, it is also possible toutilize with each step or at pre-determined intervals or for certainreasons the above described process with additional utilization of theplunger coil unit signal.

Explanation of a simple process for the determination of a permissiblecoding is given below, taking into account all requirements mentioned inclaim 2:

In a first step all possible sequences of p-sequential words areascertained and arranged in a table.

In the second step all inadmissible sequences are eliminated accordingto the conditions for step recognition and recognition of changes in themovement direction.

In a third step a random sequence is selected as starting value.

In a fourth step, this sequence is stricken from the prepared table. Themirror-image sequence is likewise stricken.

In a fifth step, the p−1 last words W_(i+1), W_(i+p−2), W_(i+p−1), ofthe last selected sequence are selected as the p−1 first words W_(i),W_(i+1), . . . , W_(i+p−2) of the succeeding sequence of coding and asequence is selected from the remaining possibilities in the preparedtable, which has the same p−1 first words. The selected sequence isagain stricken, the same as the mirror-image sequence.

Said fifth step is repeated until an adequate coding length has beenreached or until all available sequences have been used. Whereappropriate, the starting value or the selection criterion, which isselected from among several possible p-measures, may be altered in casethe process should break off prematurely.

In case of cascading of several coding areas, adherence to conditions atthe interfaces can be checked or secured “by hand”.

The following contains an explanation of another, not represented,specific embodiment for a digital absolute value transmitter. In thisspecific embodiment, in order to avoid problems with respect to steprecognition by undefined transition conditions at the boundaries ofadjacent words, a track of coding may be designed in such manner that insaid track is formed an alternating sequence of values logical “zero”and logical “one”. Based on that information, step recognition can thentake place by means of scanning said track by two, in scanning directionstaggered detectors (preferably by half a step) via appropriateevaluation of sensor signals in the evaluation unit. The evaluation unitcan then, at a “safe point in time”, trigger a scanning of therespective digital word. In addition, the evaluation unit is able toestablish from the phase displacement of the signals (using theknowledge of the arrangement of the detectors) recognition of ofdirection of rotation and also recognition of a change in the directionof rotation.

As a result of the requirement of an alternating sequence of “zero” and“one” in one of the tracks of the coding, however, the availablesequences of p-digital words, which are clearly defined within oneregion, are clearly lower than with the previously representedvariation. This applies at least in the event that one wanted to observeall the aforementioned requirements with respect to the coding.

In the event, however, that recognition of the direction of rotation orrecognition of a change in the direction of rotation takes place byevaluation of signals of the detectors then, within one uniquely definedregion of the coding, there may also exist for one, several or all(nested) sequences of p-digital words the respective mirror-imagesequence. As a result of the known rotational direction, the evaluationunit knows, even with utilization of a FiFo-register (and therewithrelated identical detected p-measures, during overtravel of a certainsequence from the one direction and during overtravel of themirror-image from the other direction) which sequence is involved withinthe uniquely defined area.

In order to have the greatest possible coding length within one uniquelydefined area, one naturally will use also for all or almost allsequences the respective mirror-image sequence.

In another specific embodiment one can, of course, also use in additionto the m track of the digital words another track with alternatingsequences of “zero” and “one”, which is scanned with two additionaldetectors. The step recognition or the recognition of the rotationaldirection or of a change in rotation direction is thereby de-coupledfrom the coding.

What is claimed is:
 1. An absolute value transmitter, comprising: atransmitter component including a coding having a predetermined number nof locally sequential digital words (W_(i)), each having a width of mindividual bits (b₁, b₂, . . . b_(m)) in adjacent tracks; at least onedetector simultaneously registering the individual bits (b₁, b₂, . . .b_(m)) defining one of the digital words (W_(i)), the transmittercomponent being movable with respect to the at least one detector; andan evaluation unit for receiving respective signals from the at leastone detector and determining an absolute position of the transmittercomponent relative to at least the one detector, at least for a firsttime, by evaluating a predetermined number p of the sequentiallydetected digital words (W_(i)), the evaluation unit assigning to adetected p-tuple (W_(i), W_(i+1), W_(i+p−1)), including a predeterminednumber p of the sequentially detected digital words (W_(i)), a definedposition value of the transmitter component relative to the at least onedetector, all of the sequences (W_(i), W_(i+1), W_(i+p−1)) from thepredetermined number p including the sequential words (W_(i)) beinguniquely defined within at least one predetermined uniquely defined area(I, II) of the coding, and the digital words (W_(i)) not being uniquelydefined within each of the at least one uniquely defined areas (I, II).2. The absolute value transmitter as set forth in claim 1, wherein thecoding satisfies at least one of a group of conditions including: a) twoof the respective adjacent words (W_(i), W_(i+1)) having differentvalues; b) each of the words (W_(i−1)) and (W_(i+1)), respectivelyadjacent to the word (W_(i)), having different values; and c) nosequence (W_(i), W_(i+1), . . . , W_(i+p−1)) existing as a mirror-imagesequence (W_(i+p−1), . . . , W_(i+1), W_(i)), within at least the oneuniquely defined area (I, II) of the coding.
 3. The absolute valuetransmitter as set forth in claim 2, wherein the evaluation unitascertains a direction of an absolute movement by comparing one of thedetected p-tuples with a stored image of the coding for complying withthe condition c).
 4. The absolute value transmitter as set forth inclaim 2, wherein the coding on the transmitter component includes the atleast two connected areas (I, II), each of the at least two connectedareas (I, II) having the predetermined number n of the digital words(W_(i)).
 5. The absolute value transmitter as set forth in claim 4,wherein the group of conditions are satisfied, at least at one of twointerfaces of the two areas (I, II).
 6. The absolute value transmitteras set forth in claim 1, wherein the evaluation unit determines theabsolute position of the transmitter component relative to at least theone detector by respectively assigning the corresponding position valueto the detected p-tuple (W_(i), W_(i+1), . . . , W_(i+p−1)).
 7. Theabsolute value transmitter as set forth in claim 6, wherein theevaluation unit determines, after a one-time determination of theabsolute position, a future absolute position of the transmittercomponent relative to at least the one detector via at least one ofincrementing and decrementing the one-time determined position value. 8.The absolute value transmitter as set forth in claim 1, wherein theevaluation unit ascertains a change in a rotational direction bycomparing the digital words W_(p−3) and W_(p−1) of the detected p-tupleand detects, if W_(p−3) and W_(p−1) are equal, a change in therotational direction following an over-travel of the digital wordW_(p−2).
 9. The absolute value transmitter as set forth in claim 1,wherein the evaluation unit determines the absolute position by: 1)generating a first output via incrementing/decrementing a prior value;and 2) generating a second output via evaluating an appropriate detectedp-tuple, the evaluation unit generating an error signal if the first andsecond outputs are not equal.
 10. The absolute value transmitter as setforth in claim 1, wherein: the width m of the digital words (W_(i))equals three; and the predetermined number p of the sequential words forthe position determination equals three.
 11. The absolute valuetransmitter as set forth in claim 1, wherein for recognizing at leastone of a rotational direction, a change in the rotational direction, anda step, one of a) a supplemental track is provided, in addition to theadjacent tracks for the digital words (W_(i)), having a sequentialseries of values including logical “zeros” and logical “ones”, and b)one of the adjacent tracks includes the sequential series of valuesincluding the logical “zeros” and the logical “ones”.
 12. The absolutevalue transmitter as set forth in claim 11, wherein: two detectors,staggered by a half step, are provided for scanning the track includingthe alternating sequences of the logical “zeros” and the logical “ones”;and the evaluation unit determines at least one of the rotationaldirection and the change in the rotational direction from a phasedisplacement of respective ones of the signals.
 13. The absolute valuetransmitter as set forth in claim 12, wherein: within the at least oneuniquely defined area (I, II), a respective mirror-image sequence(W_(i+p−1), . . . , W_(i+1), W_(i)) exists for at least one of thesequences (W_(i), W_(i+1), . . . , W_(i+p−1)) of coding; and theevaluation unit determines the absolute value from the rotationaldirection and the detected p-tuple.
 14. The absolute value transmitteras set forth in claim 1, wherein: a registration device determines anapproximate registration of the absolute position, the approximateregistration being more accurate than a difference of valuescorresponding to two limits for each of at least the two areas (I, II);and the evaluation unit, for determining the absolute position withinthe entire coding, determining an approximate absolute position valuevia the registration device and determining the absolute position valueas a function of the respective signals provided by the at least onedetector, the absolute position value being multi-valued.
 15. Theabsolute value transmitter as set forth in claim 14, wherein theevaluation unit: determines an actual signal (S_(T)) of the registrationdevice indicating an approximate registration of a correspondingposition value (α_(a)); determines a lower barrier (α_(a)−δ) and anupper barrier (α_(a)+δ) of a permissible tolerance range for thecorresponding position value (α_(a)), a width (2δ) of the tolerance areabeing smaller than each of the uniquely defined areas (I, II) of thecoding of the transmitter component; determines a multi-valued positionvalue (α_(r)) by evaluating the respective signals of the at least onedetector registering the coding; and determines a corrected absolutevalue (α_(r,corr)) according to:${\alpha_{({r,{corr}})} = {{\left( {{INT}\frac{\left\lbrack {\alpha_{a} + \delta} \right\rbrack}{\alpha_{r,{m\quad a\quad x}}} \times \alpha_{r,{m\quad a\quad x}}} \right) + {\alpha_{r}\quad {for}\quad \alpha_{r}}} < \frac{\alpha_{r,\quad {m\quad a\quad x}}}{2}}},{{{and}\quad \alpha_{({r,{corr}})}} = {{\left( {{INT}\frac{\left\lbrack {\alpha_{a} - \delta} \right\rbrack}{\alpha_{r,{m\quad a\quad x}}} \times \alpha_{r,{m\quad a\quad x}}} \right) + {\alpha_{r}\quad {for}\quad \alpha_{r}}} < {\frac{\alpha_{r,\quad {m\quad a\quad x}}}{2}.}}}$


16. The absolute value transmitter as set forth in claim 15, wherein:the evaluation unit determines if the corrected absolute value(α_(r,corr)) is within the permissible tolerance range; and if an erroroccurs, the evaluation unit generates an error signal and compensatesthe registration device for the approximate registration of the absoluteposition.
 17. The absolute value transmitter as set forth in claim 16,wherein: the evaluation unit determines a difference between thedetermined absolute value (α_(a,corr)) and the corresponding positionvalue (α_(a)); and the evaluation unit writes the corresponding positionvalue (α_(a)) in a non-volatile memory, the corresponding position value(α_(a)) being read from the non-volatile memory as a corrective valuefor subsequent determinations of the corresponding position value(α_(a)).
 18. The absolute value transmitter as set forth in claim 1,wherein the transmitter component is formed as a ring.
 19. The absolutevalue transmitter as set forth in claim 18, wherein: the transmittercomponent is rotatably joined with a component, having an angle ofrotation to be registered; the coding arranged on the transmittercomponent is endless on an outer circumference of the transmittercomponent; and each interface satisfies the group of conditions.
 20. Arotation transmitter for registering a steering angle of a motorvehicle, comprising: a rotatable transmitter mechanically connected to asteering wheel; a coding, included on the transmitter, having apredetermined number n of locally sequential digital words (W_(i)), eachhaving a width of m individual bits (b₁, b₂, . . . b_(m)), in adjacenttracks; at least one detector simultaneously registering the individualbits (b₁, b_(2, . . . b) _(m)) defining one of the digital words(W_(i)), the transmitter being movable with respect to the at least onedetector; a plunger device, mechanically connected to the steeringwheel, a rotational movement of the steering wheel causing acorresponding translational movement of the plunger device, forindicating an approximate registration of the absolute steering angle;and an evaluation unit for receiving a signal from the plunger deviceand respective signals from the at least one detector for determining anabsolute position of the transmitter relative to the at least onedetector, at least for a first time, by evaluating a the approximateregistration of the absolute steering angle anti the predeterminednumber p of the sequentially detected digital words (W_(i)), theevaluation unit assigning to a detected p-tuple (W_(i), W_(i+1),W_(i+p−1)), including a predetermined number p of the sequentiallydetected digital words (W_(i)), a defined position value of thetransmitter relative to the at least one detector, all of the sequences(W_(i), W_(i+1), W_(i+p−1)) from the predetermined number p includingthe sequential words (W_(i)) being uniquely defined within at least onepredetermined uniquely defined area (I, II) of the coding, and thedigital words (W_(i)) not being uniquely defined within each of the atleast one uniquely defined areas (I, II).
 21. A method for registering asteering angle of a motor vehicle, comprising: determining a coding on atransmitter component using at least one detector for simultaneouslyregistering individual bits (b₁, b₂, . . . b_(m)) defining respectivedigital words (W_(i)), the transmitter component being movable withrespect to the at least one detector, the coding including apredetermined number n of locally sequential digital words (W_(i)), eachhaving a width of the m individual bits (b₁, b₂, . . . b_(m)), inadjacent tracks; receiving respective signals from the at least onedetector into an evaluation unit; and determining an absolute positionof the transmitter component relative to at least the one detector, atleast for a first time, by evaluating a predetermined number p of thesequentially detected digital words (W_(i)), the evaluation unitassigning to a detected p-tuple (W₁, W_(i+1), W_(i+p−1)), including apredetermined number p of the sequentially detected digital words(W_(i)), a defined position value of the transmitter component relativeto the at least one detector, all of the sequences (W_(i), W_(i+1),W_(i+p−1)) from the predetermined number p including the sequentialwords (W_(i)) being uniquely defined within at least one predetermineduniquely defined area (I, II) of the coding, and the digital words(W_(i)) not being uniquely defined within each of the at least oneuniquely defined areas (I, II).